Can not set static DNS on debian

I'm using Debian jessie and I don't have network-manager or resolvconf installed and I'm using DHCP. **DHCP with static DNS** First of all I tried editing: /etc/network/interfaces And adding this: dns-nameservers 8.8.8.8 So now interfaces file looks like this: allow-hotplug eth0 iface eth0 inet dhcp dns-nameservers 8.8.8.8 To have DHCP and static DNS at the same time, but after restarting networking.service nothing will change. when using DHCP: ps aux | grep dhcp dhclient -v -pf /run/dhclient.eth0.pid -lf /var/lib/dhcp/dhclient.eth0.leases eth0 **Manually editing** If I manually edit /etc/resolv.conf and put nameserver 8.8.8.8 there, after restarting networking.service, system DNS server changes to 8.8.8.8, but after doing a ifup: sudo ifup eth0 Again /etc/resolv.conf automatically changes to 192.168.1.1. **NetworkManager** Then I decide to use network-manager, I installed network-manager and after setting DNS server IP in default connection and reconnecting it, it works but after rebooting the system, network-manager creates a new connection with default DNS server (192.168.1.1) and automatically connects to this one. I also checked *automatically connect to this network when it is available* in correct connection, but after reboot network-manager again connects to the other one. **Reseting after 10 Hour** I somehow managed to fix this issue by changing the new connection configs, now it does not create a new connection in every boot and connects to correct connection however now after something around 10 Hours DNS server automatically changes to 192.168.1.1 and I should reconnect the connection or restart NetworkManager.service to get DNS back into 8.8.8.8. So it's not network-manager which overrides /etc/resolv.cof **Static config** After facing all these I decide to go with static configuration. First I uninstalled network-manager then I added static configuration to: /etc/network/interfaces something like this: iface eth0 inet static address 192.168.1.10 gateway 192.168.1.1 netmask 255.255.255.0 dns-nameservers 8.8.8.8 After restarting networking.service these setting will not apply to system and interface has no IP so network is unreachable too. **Turning router DHCP off** Now that I turned my router's DHCP off, static config works fine, but I need DHCP to be on for other devices. **Permission** I can edit /etc/resolv.conf and change it's permission so nobody can edit it... But I'm looking for a reason. I want to know why these are not working, which program overrides /etc/resolv.conf and what is the right way to set DNS server. Is there anything that I'm missing here?